Unity UI How do button transitions work?

Buttons can specify various color tinting for an Image based on the button state (normal/highlight/press/disabled).

If you look at the inspector while the game is running, the Image's "base" color does not change as the Button animates. If you use a very long transition time, you can even use the inspector to change the Image's color in the middle of a transition, and the Button will continue smoothly transitioning between its tints on the new base color.

How does it do that? Can I write my own custom MonoBehaviour that can modify an Image's apparent color without actually changing its "color" property?

 

yes, you can do this.
Every Graphics component (Image, RawImage, Text, ...) has two methods which you can use to do a transition:
- CrossFadeColor
- CrossFadeAlpha

They will not touch the color in the component but will change the color of the vertices anyways.